Dynamically Composing Expression Predicates

PredicateBuilder.cs

using System.Linq.Expressions;

namespace Library.Data.Linq;

//! Reference: http://www.albahari.com/nutshell/predicatebuilder.aspx
public static class PredicateBuilder
{
    public static Expression<Func<T, bool>> True<T>() => f => true;
    public static Expression<Func<T, bool>> False<T>() => f => false;

    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
        return Expression.Lambda<Func<T, bool>>(Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);
    }

    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
        return Expression.Lambda<Func<T, bool>>(Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);
    }
}

Source code is copied from C# 10 in a Nutshell